The invention relates to a device for inhaling pharmaceutical drugs by means of auxiliary positive-pressure respiration.
During normal spontaneous human breathing, inhalation occurs as the respiratory muscles actively expand the thorax, thereby creating a pressure gradient, with the result that air is drawn in, i.e. flows into the lungs in accordance with the pressure gradient. Exhaling occurs passively in that a pressure rise takes place in the lung as the thorax is restored elastically to its default position, with the result that the consumed air is expelled from the thorax and the lungs. The mean pressure level by means of which inhalation and exhalation occur alternately corresponds to the atmospheric pressure.
Under conditions of illness or disease, e.g. in the case of asthma, small and medium-sized respiratory tracts (bronchial tubes) in the lungs can become constricted. The flow resistance in them increases, particularly during exhalation, with the result that the patient is forced to work actively by means of his muscles even during exhalation. As a consequence an additional pressure increase occurs in the thorax which can result in a complete collapse of the constricted respiratory tracts and it becomes impossible to expel air from the relevant sections of the lungs (i.e. air is trapped). Such situations often occur in the form of attacks and can be acutely life-threatening for the patient (acute asthma attack).
Devices with which the patient can inhale pharmaceutical drugs himself are known in the art. These pharmaceutical drugs are generally introduced into the respiratory tracts via the mouth as an aerosol or powder inhalant by means of a nebulizer or atomizer. An advantageous embodiment has retarding chambers, such as spacers, in which a particular volume of air is enriched with aerosol or powder inhalant before being inhaled and then is made available for inhalation. This improves the effectiveness of the inhaled pharmaceutical drugs. The disadvantage of such simple, easily portable, non-electrically operated inhalation systems that can be used by the patient himself in an emergency is that they can only be operated at atmospheric pressure. Lung sections which cannot take part in spontaneous breathing because of the above-described collapse of small respiratory tracts therefore remain inaccessible at atmospheric pressure even during emergency treatment with inhaled pharmaceutical drugs.
Respiration under positive pressure is known in the art. Such methods are applied in particular in breathing apparatus used in a non-breathable atmosphere and by divers. The disadvantage of such methods is that they are not designed for patients suffering from acute breathing difficulties and are also complex, requiring valves, tubing and also, if appropriate, as with breathing apparatus with a closed breathing circuit and diving equipment, a carbon dioxide absorber to process the exhaled air which is rich in carbon dioxide. The standard positive-pressure respiration system for treating patients with severe breathing difficulties is generally in the form of complex, fixed respirators in hospital areas designed for this purpose and proceeds either automatically (mechanical respiration without action by the patient) or in assisted mode (with action by the patient), orxe2x80x94if the patient is breathing spontaneouslyxe2x80x94also via CPAP (continuous positive airway pressure). Respiration can be carried out with positive pressure either continuously or intermittently. Simple, non-electrically-operated manual devices for this purpose are not known in the art.
It is the object of this invention to provide a very simple, small, portable, easily operated, integrated, self-contained device which is independent of electrical power and is suitable in particular for asthmatics and patients with other obstructive lung diseases for temporarily improving the inhalation of pharmaceutical drugs which efficiently combines the therapeutic effect of inhaled pharmaceutical drugs, the advantages of a retarding chamber and the physical effect of positive-pressure respiration for a brief period, i.e. for the limited period of acute breathing difficulties.
In accordance with the invention a very simple, small, portable, easily operated, integrated and self-contained device is provided which can comfortably be stored in a bag, e.g. a handbag. The device consists of a closed system into which the patient can exhale without a breathing air circuit being created. By contrast with the complex respirators which operated hitherto with a closed breathing circuit and at a pressure greater than atmospheric pressure, there is no need here for the valves and tubing. Similarly, no processing of the exhaled gas, e.g. in a carbon dioxide absorber, takes place, meaning that a device in accordance with the invention is limited to a few minutes of use, i.e. to the duration of the acute breathing difficulties, because of the accumulation of carbon dioxide.
The device comprises a mouthpiece which can be fully encompassed by the lips; a reservoir which has a variable volume to accommodateinhalant gas, can be connected to the mouthpiece in the direction of flow either directly or via a distributor and provides the characteristic features of a retarding chamber; an adjustable airtight closure between the mouthpiece and the reservoir; and at least one connection for the pharmaceutical drug feed in the form of an aerosol or powder inhalant to the reservoir, with the pharmaceutical drug feed being either direct or indirect via a distributor. An essential feature is that the reservoir has a variable wall to enable it to change its volume, where said wall can be expanded under the pressure of inflowing inhalant gas against a restoring force such that, as a result of the action of the restoring force, auxiliary positive-pressure respiration occurs when the inhalant gas containing the pharmaceutical drug is inhaled.
The variable wall of the reservoir can be embodied in various ways so that it is at least partially movable, for example being formed of a combination of rigid and movable sections. In accordance with a preferred embodiment the variable wall has at least one elastic wall and an elastic balloon in particular forms the reservoir.
A further variant provides for the reservoir to have at least one rigid wall section on which a distributor and/or at least one connection for the mouthpiece, the inhalant gas filler connection or the pharmaceutical drug feed are provided.
A preferred embodiment provides for a gas reservoir with a compression-proof wall containing compressed inhalant gas to be connected to the reservoir directly or indirectly via a distributor and for a reclosable valve to be configured between the gas reservoir and the reservoir. In this device the gas reservoir is filled when in transport mode, and the reservoir, which is preferably in the form of a balloon with a floppy elastic wall, is empty. In accordance with the invention the pharmaceutical drugs are inhaled by first opening the filled gas reservoir with a compression-proof wall by means of a valve, allowing oxygen or oxygen-rich air to flow into the elastic-walled reservoir. As soon as the elastic-walled reservoir is sufficiently full, the valve between the gas reservoir with a compression-proof wall and the elastic-walled reservoir can be closed again, for example by the user. This means that, as in a balloon, the pressure in the elastic-walled reservoir is slightly higher than atmospheric pressure, at between greater than 0 and approx. 30 cm water column. This is caused by the elastic wall tension of the reservoir. Pharmaceutical drugs which act on the respiratory tracts can now be introduced into the elastic-walled reservoir, which thus takes on the function of a retarding chamber, from at least one commercially available bottle for the spray inhalation of pharmaceutical drugs. The device is now ready for use and can be used by the patient.
The patient encompasses the mouthpiece firmly with his lips, then either fits a nose clip or actively blocks his palate to prevent the physiological route for air through the nose, and then opens the airtight closure between the mouthpiece and the elastic-walled reservoir by pressing with his finger or by means of a device which automatically opens the closure when the patient first inhales. The increased pressure in the elastic-walled reservoir is also transferred to the patient""s lungs via the respiratory tracts, thereby allowing oxygen and pharmaceutical drugs to enter the patient""s lungs until the pressure gradient between the elastic-walled reservoir and the lungs has equalized. In this process oxygen and pharmaceutical drugs are also forced into those sections of the lungs which were inaccessible as a result of constricted and previously collapsed respiratory tracts at atmospheric pressure.
The lungs are therefore pre-inflated for the period that the device in accordance with the invention is in use, and the pressure in them corresponds no longer to atmospheric pressure but to the pressure set by the elasticity of the reservoir wall or by a spring device in the case of reservoir wall elements which can slide over each other. Continued inhalation and exhalation occurs, as in the case of the previous spontaneous breathing at atmospheric pressure, by alternate active muscular expansion and elastic contraction of the thorax. This counteracts the collapse of the small respiratory tracts which occurs as a result of disease and also enables those lung sections to be treated by means of inhalation which were inaccessible, i.e. were not reached by spontaneous breathing, at atmospheric pressure.
Because the patient draws inhalant gas and pharmaceutical drugs from a closed system into which he exhales again without processing of the exhaled gas, oxygen is consumed, and the carbon dioxide level is enriched. Because of the latter feature in particular, the patient must cease inhalation with the device in accordance with the invention after a short period within which the state of acute breathing difficulty should have improved.
If pharmaceutical drugs need to be inhaled again by means of auxiliary positive-pressure respiration, the consumed inhalant gas is discharged from the reservoir via the closure and the mouthpiece, and the gas reservoir is opened again via the valve. The process as described above is then repeated.
The volume and elasticity or restoration properties of the reservoir can be individually adjusted by selecting an appropriate balloon or restoration device such as a spring.
If it is decided to dispense with multiple use of the device in accordance with the invention and instead to use it only for single-use emergency treatment, the gas reservoir with a compression-proof wall in a further advantageous embodiment of the invention with improved handling only needs to contain oxygen for a single use. This enables the device to be designed such that it is even smaller and lighter, and it is also possible to dispense with a reclosable valve between the gas reservoir with a compression-proof wall and the reservoir with a variable wall. In this case, however, a new gas reservoir must be fitted before each new use.
The central functional element of the invention is the reservoir with a variable or at least partially elastic wall which is both responsible for the respiration pressure and also, like a retarding chamber, delivers a certain volume of inhalant gas which is enriched with aerosol or powder inhalant before being inhaled. Various practical embodiments of the invention are possible; in particular, the various elements of the device in accordance with the invention can either be connected separately to a central distributor or, like a set of bagpipes, the mouthpiece and the connections for the gas reservoir with a compression-proof wall and the bottles for the spray inhalation of pharmaceutical drugs can open directly into the elastic-walled reservoir.